Liquid fuel supply system



was.

Deg 20, 1960 2,965,086

J. B. GREGORY EIAL LIQUID FUEL SUPPLY SYSTEM Filed Sept. 25, 1959 4Sheets-Sheet l AIR CLEANER /4 F051. PUMP Fla 1 //V VEA/ 7' 0195 JAMESls. GREGORY HOWARD 0. 5445250 CHARLES C. MOORE /liw infl v Decrzo, 1960J. B. GREGORY ET AL 2,965,086

LIQUID FUEL SUPPLY SYSTEM I Filed Sept. 25, 1959 4 Sheets-Sheet 5 40? CAW/VER EODY 7'0 I/AIICUUM /A/I/E'/V7'0/?5 F054 PRESSURE M44455 6.6/?5604? EEGUAATOR Han 44 0 a 5415mm 09 4/94 55 c. Mao/8 Dec. 20, 1960J. B. GREGORY ETAL LIQUID FUEL SUPPLY SYSTEM Filed Sept. 25, 1959 4Sheets-Sheet 4 4/): c4 EAA/ER A'Z/EL Pam/p MAME-5 5. 6%.560/9/ Han 4R00. s/wwsa/v #42455 c. 4/0045 United States LIQUID FUEL SUPPLY SYSTEMJames B. Gregory, Howard D. Emerson, and Charles C.

Moore, Fullerton, Calif., assignors to Union Oil Company of California,Los Angeles, Calif., a corporation of California Filed Sept. 25, 1959,Ser. No. 842,262

22 Claims. (Cl. 123-136) This invention relates to the abatement of airpollu tion, and in particular concerns certain new and usefulimprovements in fuel systems for internal combustion engines, such asthose employed for the propulsion of motor vehicles.

The operation of motor vehicles contributes markedly to the airpollution problem in large cities by the release of hydrocarbons to theatmosphere, either as unburned fuel via the exhaust system, or asevaporated fuel via the fuel supply system. A great deal of evaporatedfuel originates from the motor vehicle engine carburetor both duringperiods of operation and non-operation. One of the major sources ofthese carburetor evaporation losses is from the carburetor float bowl,which is a vented reservoir of volatile fuel constantly exposed to heatfrom both the atmosphere and the engine. These evaporative losses areessentially a function of fuel volatility, float bowl temperature, andcarburetor design.

Fuel vapors from the conventional float bowl can escape to theatmosphere along two principle routes: (1) directly to the atmospherethrough external vents in the float bowl, and (2) through so-calledinternal vents or balancing tubes into the throat of the carburetor.When the engine is running, hydrocarbon vapors escaping through theinternal vents are drawn into the combustion chamber with incoming airand subsequently combusted. However, any vapors that escape through theexternal vents during this operational period will contaminate theatmosphere. When the engine is turned off hydrocarbon vapors escapethrough both the internal and external vents to the atmosphere. However,since carburetors perform at widely varying temperatures with volatilefuels, some form of venting must be used to keep the float bowl atessentially the same pressure as the other communicating carburetorchambers when the engine is running.

One major cause of carburetor evaporation loss, only casually consideredby previous investigators, is the so called carburetor hot soak whichbegins immediately after the engine is turned off. Heat stored by theengine while running is transmitted to the carburetor float bowl, which,depending on design, normally contains from around 80 to 200 ml. ofvolatile hydrocarbon fuel. As the trapped fuel in the float bowl isheated evaporation occurs through the aforementioned carburetor vents.Generally, there is a float bowl temperature rise of from about 40 to 60F. from the bowl temperature at the time the engine is shut off to thepeak temperature reached (usually in about 20 to 40 minutes) during thehot soak period. It can be generally stated that atmospherictemperatures have little effect upon the hot soak temperature of thecarburetor bowl; the bowl tempera ture seems to be controlled primarilyby engine coolant temperature. Carburetor design has virtually no effecton hot soak losses, except in the matter of float bowl fuel capacity. Ithas been found that normal losses to the atmosphere from the carburetorfloat bowl during the hot soak period range from to 30 percent of2,965,086 Patented Dec. 20, 1960 n; to the fuel remaining in the floatbowl at the time the engine is stopped.

It is accordingly an object of this invention to provide an improvedmethod and apparatus for the abatement of atmospheric pollutionresulting from the operation of internal combustion engines.

Another object is to provide an improved method and apparatus foreffecting a substantial reduction in the gross fuel consumption ofautomobiles, thus resulting in more eflicient and economical operation.

A further object is to reduce substantially the evaporative fuel lossesfrom the fuel supply system of internal combustion engines.

Other and related objects will be apparent from the detailed descriptionof the invention, and various advantages not specifically referred toherein will be apparent to those skilled in the art on employment of theinvention in practice.

We have now found that the foregoing objects and their attendantadvantages can be realized in a conventional internal combustion engine,such as is used in the propulsion of motor vehicles, by providing thefloat bowl of a conventional carburetor with a fuel drain line whichempties the fuel remaining in the carburetor float bowl to an alternatereservoir as soon as the engine is stopped. This removes the highlyvolatile hydrocarbons from the high temperature environment of thecarburetor float bowl before any significant losses from hot soak canoccur, thus eliminating a major source of air pollution.

The invention will be more readily understood by reference to theaccompanying drawings which form a part of this application. Figure l isa schematic diagram of one of the simplest embodiments of thisinvention. Figure 2 is a schematic diagram of the apparatus of thisinvention in one of its preferred embodiments. Figure 3 is a furthermodification of the apparatus of Figure 2 wherein the tank vent isclosed to the atmosphere at all times except when the float bowl isemptying. Figure 4 is a schematic diagram of another embodiment of theinvention wherein the fuel tank is vented only during engine operation.Figure 5 is a modification of Figure 1 wherein the drain line includes adrain level assembly. It is to be understood that although the floatbowl draining method and apparatus is broadly applicable to any internalcombustion engine using a volatile fuel and a fuel induction system, itis particularly useful for gasoline-burning engines, such as those usedin automobiles, trucks, buses and the like. However, it also haspractical use with engines using somewhat heavier fuels such as dieselengines, jet engines, and the like.

Referring now more particularly to Figure 1, the apparatus there shownconsists essentially of the fuel supply system for an internalcombustion engine. The fuel supply enters fuel tank 10 via inlet conduit36. When fuel tank 10 has an adequate supply of volatile fuel, tank cap38 seals inlet conduit 36. Tank vent 42 communicates with the atmosphereand, as is conventional with fuel storage tanks on motor vehicles,maintains fuel tank 10 at atmospheric pressure. Fuel is supplied tocarburetor float bowl 18 via line 12, fuel pump 14, and line 16. Fuelpump 14 can be any of the conventional pumps used in the fuel supplysystems of internal combustion engines such as a vacuum-operated fuelpump, an electrical pump, a mechanical pump, or the like. However, fuelpump 14 is preferably electrically operated so that operation thereofcan start immediately when the ignition is turned on, thus filling floatbowl l8 rapidly and independently of engine operation. The fuel enterscarburetor float bowl 318 at a rate controlled by the characteristics offuel pump 14 and float valve 28 which, as it rises, restricts the outletof line 16 into carburetor float bowl 18, thus acting as a liquid levelcontrol device to maintain a substantially constant level of fuel withincarburetor float bowl 18.

The foregoing constitute conventional elements found in nearly allcarburetor fuel supply systems. According to our invention, a novel fuelreturn system is provided in the form of a return line 30, opening fromthe bottom of bowl 18, and communicating in fuel delivery relationshipwith fuel tank 10 via drain valve 32 and line 34. Valve 32 can belocated at any intermediate horizontal level between the inlet to line30 and the outlet of line 34, but for convenience of access ispreferably located immediately below the carburetor body 20. Returnlines 30 and 34 can be constructed of A: or 4 inch LD. tubing, such asis used for conventional fuel delivery lines. However, as will be morefully explained below, a suitable restriction to flow is incorporatedinto the fuel return system so that fuel from bowl 18 will not bereturned to tank 10 at a faster rate than the supply system can deliverfuel to float bowl 18.

One method of operating the apparatus as shown in Figure 1 is to havedrain valve 32 ina blocked open position. There is then a constantlyopen drain line from float bowl 18 to fuel tank 10, both when the engineis operating and when the engine is stopped. With drain valve 32 blockedopen and the engine running, fuel is continuously pumped from fuel tank10 via fuel pump 14 to float bowl 18. Simultaneously, fuel is constantlyflowing from float bowl 18 to fuel tank 10 via line 30, blocked opendrain valve 32 and line 34. Thus, there is a constantly circulating flowof fuel from fuel tank 10 to carburetor float bowl 18 and back to fueltank 10, with an adequate reservoir level in carburetor float bowl 18being maintained by float valve 28. The drainage capacity of the fuelreturn system comprising line 30, valve 32 and line 34 is such that theflow through this return system is small compared to the total capacityof the fuel supply system. Typically, the rate of gravity flow throughthe return system is about to /2 of the flow capacity of the fuel supplysystem to the carburetor.

At no time during engine operation can there be allowed an excessivefloat bowl drainage so that the reservoir will be depleted to aninoperable point or to a level which will detrimentally affect normaloperation. This drainage or return flow can be adjusted to the desiredlevel by manipulation of drain valve 32. Alternatively, drain valve 32can be replaced by an appropriate orifice which will restrict returnflow so as to maintain an adequate fuel supply in carburetor float bowl18 during all conditions of engine operation. Other methods ofrestricting flow are also satisfactory such as the use of a capillarytube drain line or any small size line having sufficiently smallerdrainage flow capacity than the delivery capacity of the fuel supplysystem to maintain adequate operating fuel level in float bowl 18 duringengine operation. A restriction such as an orifice, the partial closingof drain valve 32, or a small diameter drain line will occasionallyserve to prevent reverse surge in the drain line from the fuel tankduring downhill driving or rapid stops, resulting in overfilling ofcarburetor bowl 18.

When the engine is stopped, fuel pump 14 no longer delivers fuel, as itis controlled by the engine operation. Carburetor float bowl 18 is thenquickly emptied of fuel via line 30, drain valve 32 and line 34. Thus,with the above-described mode of operation there is little fuel loss tothe atmosphere through external vent 22 of carburetor float bowl 18since the highly volatile fuel has been removed from the float bowlwithin a few seconds to 3 or 4 minutes after the engine is stopped. Whenoperation of the car is resumed fuel pump 14 quickly introduces fuel ashereinbefore described to carburetor float bowl 18, thus restoring thefuel therein to an adequate level for engine operation.

Line 34 can enter fuel tank either in th 2 space at the top of the fueltank or, as shown in Figure 1, the drained fuel from carburetor floatbowl 18 can return to the bottom of fuel tank 10. Since this drainagefuel is usually warmer than the fuel in the fuel tank because of passingthrough the carburetor and the engine compartment, the Figure lembodiment reduces evaporative fuel flashing by introducing saiddrainage fuel into the bottom of the cool body of fuel in tank 10.However, with some fuel systems it is preferred to bring fuel drain line34 into the highest and most remote point of fuel tank 10. Thisintroduction of the fuel drain line into a relatively permanent vaporspace above the body of fuel in tank 10 prevents any possibility ofreverse drainage from fuel tank 10 to float bowl 18 when the vehicleassociated with the engine is stopped on a steep incline. A preferredlocation for the fuel return, i.e., through line 34, is into the vaporspace of inlet conduit 36 which is ordinarily free of any liquid level.

Further modifications of the apparatus which have been highly successfulin reducing evaporation loss, particularly during engine operation,involve the closing of external vent 22 by means of a plug or some otherappropriate vapor-tight closure. We have found that if the fuel drainline of our invention is used with an internal combustion engine, thenexternal vent 22 can be plugged with no change in the normalsatisfactory operation of the engine. A large variety of conventionalcarburetors have been operated with plugged external vents for extendedperiods of time in combination with the method and apparatus of ourinvention with a high degree of success. Evaporation losses from thefuel system were materially reduced, with a resultant reduction inatmospheric pollution and in gross fuel consumption. It has been foundthat as a further means of reducing evaporate losses of volatile fuels,fuel tank 10 should be insulated to reduce the acquisition of heat, thuslowering the temperature of the fuel contained therein. By means of tankinsulation there is a reduced temperature rise during motor vehicleoperation, which thus reduces the vapor pressure of the fuel andeffectively reduces the evaporation losses from the fuel tank itselfthrough tank vent 42. Any conventional insulating material can be usedsuch as glasswool, asbestos, and the like. Also, a reflective surface onthe fuel tank such as a white or aluminized undercoating is useful inreducing heat acquisition from hot pavements.

A further modification of the apparatus of Figure 1 entails connectingtank vent 42 of the fuel tank 10 to external vent 22 of float bowl 18.Thus, there is communication between the vapor space of fuel tank 10 andthe vapor space of float bowl 18 which, during engine operation, willpermit any vapors evaporating from fuel tank 10 to pass through tankvent 42 to float bowl 18 and thence through internal vent 24 to thethroat of the carburetor where these vapors are swept into the enginecombustion chamber and burned. Tank vent 42 can also be returned to aircleaner 26 or to any air intake channel of carburetor 20 where fuelvapors from fuel tank 10 are carried into the combustion chamber of theinternal combustion engine during engine operation. When tank vent 42 isreturned to an air intake channel in the fuel induction assembly therewill be occasional fuel condensation within tank vent 42. In this case,tank vent 42 should either be located and designed to drain freely orsuflicient heat should be provided to vaporize any condensate formed.Because of the problems entailed in passenger car design, gravitydrainage of condensate from a vent line communicating between tank vent42 and the fuel induction assembly can be attained only by passing sucha vent line up from the gas tank and just under the car roof to thefront of the automobile where the vent line can then descend into theengine compartment and subsequently to the fuel induction assembly.However, if it is necessary for design considerations to construct dipsor loops into the conduit system, as when run underneath the automobilebody, then a heat source should be provided over the entire conduitlength or at least at the low points to vaporize condensate that mayoccur. The vent line can be traced with an exhaust gas conductingconduit or an electrical resistance tracing to provide a heat source.Also, since the low point in many vapor conduit systems will runparallel to the exhaust gas mufller and pipes, the vent line can be runadjacent thereto and thus derive sufficient heat to stay condensatefree. When the engine is stopped the same vapor path exists whichmaintains float bowl 18 and fuel tank 10 at substantially the samepressure thus permitting easy draining of float bowl 18.

Return lines 30 and 34 can become vapor locked under certain designconditions, i.e., when said lines are not in continuous descent to fueltank 10, and/or do not have suflicient size to relieve themselves of thegas or vapor which occupies this line space after the carburetor bowlhas drained. This vapor locking, of course, occurs only if line 34drains into the liquid body of tank 10, and is thus eliminated when line34 communicates with the vapor space of tank 10. To relieve thisproblem, we may provide one or more atmospheric vents which, when engineoperation is resumed, serve to release trapped vapors, thus priming thelines for satisfactory operation. Vent line 40 is such a conduit forventing the drain-back system. As shown in Figure 1, vent 40 can bereturned to the air cleaner assembly to prevent the escape of volatilefuel vapors into the atmosphere during engine operation, or it can bevented directly to the atmosphere if desired. The location of vent 40 inthe fuel drain-back conduit is not critical as long as it allows gas toescape from the conduit for effective draining. The outlet of any suchvents should preferably be located above the level of the fuel in floatbowl 18.

An alternate method of operation of the apparatus shown in Figure 1comprises starting the engine operation with drain valve 32 closed andcarburetor float bowl 18 empty. Fuel is supplied to carburetor floatbowl 18 as hereinbefore described, which fills and maintains an adequatefuel reservoir through the action of float valve 28. There is no flow ofgasoline through the system comprising line 30, drain valve 32 and line34 during engine operation. When the engine is stopped fuel pump 14stops and therefore no longer supplies fuel via line 16 to carburetorfloat bowl 18. Drain valve 32 is immediately opened upon engine stoppageand float bowl 18 is drained of its fuel content via line 30, drainvalve 32 and line 34 to fuel tank 10. Drain valve 32 is then closd priorto or coincident with resumption of engine operation. The opening andclosing of drain valve 32 can be effected by the engine intake manifoldvacuum if it is a vacuum actuated valve, or by the ignition switch if asolenoid actuated valve, or manually if a conventional mechanical valve.The opening and closing of such valves is conventional and well-known inthe art and hence need not be described in detail.

Referring now more particularly to Figure 2, the apparatus here showncomprises a preferred embodiment of our fuel supply system. The volatilehydrocarbon fuel enters fuel tank 100 via inlet conduit 124. The outersurface of fuel tank 100 is covered with about one inch of glasswoolinsulation 160. When fuel tank 100 is filled to the desired level, tankcap 126 seals inlet conduit 124. Tank cap 126 is a conventional pressurerelief cap which maintains the fuel tank under a positive pressurebetween about 0 and about 2 p.s.i.g. The design of these so-calledpressure caps is such that when the pressure within the fuel tank fallsbelow atmospheric, a check valve 127 in the fuel cap opens so that it isimpossible for vacuum to develop within fuel tank 100. When pressuresabove about 2 p.s.i.g. develop, a relief valve 125 is opened to reducethe pressure to about 2 p.s.i.g. The fuel from tank 100 is supplied tocarburetor float bowl 108 via line 102, fuel pump 104, fuel pressureregulator 105, and line 106. Fuel pump 104 in this preferred embodimentis an electrically operated pump which operates whenever the ignition ison and ceases operation, thus blocking the passage of fuel, when theignition is off. Fuel pump 104, however, could be a conventionalvacuum-operated fuel pump or a mechanical pump or the like. Conventionalfuel pressure regulator 105 is an optional element of the fuel systemwhose use is dictated by the fuel pump used, the operating pressure ofthe fuel tank, and similar considerations. Normally these pressureregulators operate at between about 1 p.s.i.g. and about 5 p.s.i.g. fuelpressure to the carburetor. The fuel enters carburetor float bowl 108from line 106 at a rate controlled by the pressure setting of fuelpressure regulator 105 and conventional float valve 116 which, as thefuel within float bowl 108 rises, restricts the entrance of line 106into float bowl 108 and thus acts as a metering device to maintain asubstantially constant level of fuel within carburetor float bowl 108.

The fuel drain-back system comprises line 118 opening from the bottom offloat bowl 108, vacuum operated drain valve 120, and line 122 whichopens into fuel tank 100. Fuel tank 100 is in communication with theatmosphere via line 128, vacuum operated vent valve 130 and conduit 132.The operation of valve 120 in the fuel drain-back system is controlledby a vacuum delay system comprising conduit 136, a small vacuumreservoir tank 138 provided with orifice 146, conduit 140, check valve142, and vacuum supply conduit 144.

The operation of the fuel supply system of this preferred embodimentstarts with the initial filling through inlet conduit 124 of fuel tank100 until the desired fuel level is obtained. Pressure cap 126 is thensecured thus sealing the end of inlet conduit 124. Prior to starting theinternal combustion engine of which this fuel supply system is a part,valve 130 is open and valve 120 is open. When the engine is started thevacuum actuated valves 120 and 130close, and fuel is supplied tocarburetor float bowl'108 via line 102, fuel pump 104, fuel pressureregulator 105, and line 106. Float bowl 108 is quickly filled to theoperative level as controlled by float valve 116. During the period ofengine operation, valve 120 and 130 remain closed. Keeping valve 130closed prevents the escape of fuel vapors from the tank vent line 132 tothe atmosphere, which, due to the slopping of the fuel within the tankcan be an appreciable source of hydrocarbon contaminant in theatmosphere. During engine operation any vapors which develop infloat'bowl 108 travel via internal vent 112 in carburetor body to theother carburetor chambers and are thus swept into the combustionchambers of the engine and burned.

When the engine is shut off the conventional vacuum manifold of theinternal combustion engine returns to atmospheric pressure, thusdissipating the vacuum source which was holding valves and closed, andvalve 130 opens immediately allowing tank 100 to come to atmosphericpressure. The opening of valve 120, how ever, is delayed by the actionof vacuum reservoir tank 138. In a fuel system as herein described, itis necessary that tank 100 be near or at the same pressure as float bowl108 when drain valve 120 is opened. Otherwise, there could be a reversesurge of fuel into float bowl 108 which would prevent proper drainage,and might even overflow into the engine compartment resulting inexcessive hydrocarbon loss to the atmosphere. When the engine vacuummanifold returns to atmospheric pressure, check valve 142 automaticallycloses thus allowing vacuum reservoir tank 138 to come gradually toatmospheric pressure by the entrance of air through orifice 146. Thedelay in opening valve 120 is thus a function of the size of orifice 146and a vacuum reservoir tank 138. Atypical system has a time delay ofabout 15 seconds, and comprises a vacuum reservoir volume of about 32cubic inches and an orifice diameter of about 0.02 inch. Obviously,however, any

other combination of orifice size and vacuum reservoir volume whichwould give the desired time delay could be used. Operative time delayperiods of about 3 to 60 seconds are contemplated.

When the pressure in vacuum reservoir tank 138 approaches atmospheric,valve 120 opens and permits the fuel remaining in carburetor float bowl108 to drain back to fuel tank 100 via line 118, opened drain valve 120and line 122. Line 118 is supplied with an optional atmospheric vent 150to air cleaner 114, which as previously discussed with respect to Figure1, allows the escape of trapped air and vapors in the drain-back conduitsystem. When the engine is restarted, valves 120 and 130 close by actionof the engine vacuum source,

and the system repeats the first described mode of operation.

The fuel system as above described is not limited to the use of vacuumactuated valves. Valves 120 and 130 can be electrical solenoid valveswith appropriate circuiting, usually in conjunction with the ignitioncircuit. Thus, valves 120 and 130 would be held open when the ignitionis off and held closed when the ignition is turned on. Instead of thevacuum delay system used to control valve 120, we may also use aconventional mechanical or electrical delay system. Valves 120 and 130may also be mechanical valves operated manually.

Referring now more particularly to Figure 3, the apparatus here shown isa fragmentary view of the fuel supply system of Figure 2 with a modifiedfuel tank venting apparatus therein. The apparatus of Figure 3 isidentical in every respect to Figure 2 with the following exceptions.The operation of valve 130 is controlled by a time delay systemcomprising line 134, valve 170 with its own vacuum supply line 172, line174, vacuum reservoir 176 with orifice 178, line 180, check valve 182and vacuum supply line 184. The operation of the apparatus of Figure 3is identical to the operation of the apparatus of Figure 2 with theexception of the venting of fuel tank 100.

Prior to the starting of the internal combusion engine of which thisfuel supply system is a part, valve 130 is closed and valve 170 is open.When the engine is started vacuum-operated valve 170 closes therebyisolating the control side of valve 130 from its vacuum source and thusmaintains valve 130 closed during engine operation. When the engine isshut off, the conventional vacuum manifold of the internal combustionengine returns to atmospheric pressure thus dissipating the vacuumsource which was holding valve 170 closed. Valve 170 hence opensimmediately and allows valve 130 to communicate with the vacuum sourcerepresented by the vacuum reservoir tank 176. This immediately opensvalve 130 and vents fuel tank 100 to the atmosphere. The closing ofvalve 130 is delayed, however, by the action of vacuum reservoir tank176. In a fuel system as herein described, it is necessary that tank 100be near or at the same pressure as float bowl 108 when drain valve 120is open. When the engine vacuum manifold returns to atmosphericpressure, check valve 182 automatically closes thus allowing vacuumreservoir tank 176 to come gradually to atmospheric pressure by theentrance of air through orifice 178. The delay in the closing of valve130"is thus a function of the size of orifice 178 and vacuum reservoirtank 17 6 as previously discussed in relation to the vacuum delaycontrol system for valve 120. When the pressure in vacuum reservoir tank176 approaches atmospheric, valve 130 closes and prevents any furthervapor loss from fuel tank 100 during the engine-off period. It isnecessary that the closing of valve 130 be closely coordinated with thedraining of float bowl 108. The time delay should be such that floatbowl 108 is completely drained before the closing of tank vent valve130. Thus, with the modification of Figure 3, fuel tank 100 is preventedfrom losing vapor to the atmosphere except during the very short periodof time required to drain float bowl 108. As previously discussed, thevacuum-operated valves in Figure 3 can also be mechanically orelectrically operated and the time delay system controlling valve 130can also be a conventional mechanical delay, electrical delay, or

the like.

Referring now more particularly to Figure 4, the apparatus there showncomprises another embodiment of our float bowl draining system. Thevolatile hydrocarbon fuel enters fuel tank 200 via inlet conduit 226.The outer surface of fuel tank 200 is covered with insulation 201comprising two layers of heavy asbestos paper, one layer of aluminumfoil and an outer layer of asbestos cloth. The entire insulationthickness is approximately /2 inch. When fuel tank 200 is filled to thedesired level, tank cap 230 seals inlet conduit 226. Tank cap 230 is aconventional pressure relief cap comprising a check valve 232 whichmaintains the fuel tank under a positive pressure between about 0 andabout 2 p.s.i.g. and a check valve 232 which opens when the pressurewithin the fuel tank falls below atmospheric so that it is impossiblefor a vacuum to develop within fuel tank 200. The fuel from tank 200 issupplied to carburetor float bowl 210 via line 202, fuel pump 204, line205, fuel pressure regulator 206 and line 208. Fuel pump 204 in thisembodiment is an electrically operated pump which functions whenever theignition is on and ceases operation, thereby blocking the passage offuel, when the ignition is off. Fuel pump 204 could, however, be aconventional vacuum operated fuel pump or a mechanical pump or the like.Conventional fuel pressure regulator 206 is an optional element of thefuel system identical to regulator of Figure 2, previously discussed indetail. The fuel enters carburetor float bowl 210 from line 208 at arate controlled by the pressure setting of fuel pressure regulator 206and conventional float valve 218 which, as the fuel within float bowl210 rises, restricts the line 208 entry to float bowl 210 and thus actsas a metering device to maintain a substantial constant level of fuelwithin carbu retor float bowl 210.

In the present modification of our invention the fuel drain-back systemcomprises a line 220 opening from the bottom of float bowl 210, vacuumoperated drain valve 221, line 222, valve 223 and line 224 whichcommunicates with the permanent vapor space in fuel tank 200 via inletconduit 226. Fuel tank 200 is in communication With the atmosphere vialine 234, vacuum operated vent valve 236-, and conduit 238 which opensinto the vapor space of float bowl 210. The latter is maintainedessentially at atmospheric pressure via internal vent 214 in carburetorbody 212 and air cleaner 216. The operation of valve 221 in the fueldrain-back system is controlled by a vacuum delay system comprisingconduit 242, a small vacuum reservoir tank 244 provided with orifice252, conduit 246, check valve 248 and vacuum supply conduit 250. Vacuumoperated vent valve 236 is controlled by the same delay system as valve221 and communicates therewith via line 240.

The operation of this fuel supply system entails filling fuel tank 200through inlet conduit 226 with liquid fuel until a desired level isobtained. Pressure cap 230 is then secured to conduit 226 sealing theend thereof. Prior to starting the internal combustion engine of whichthis particular fuel supply system is a part, valves 221 and 236 areclosed and valve 223 is open. When the engine is started vacuum actuatedvalves 221 and 236 open and valve 223 closes, and fuel is supplied tocarburetor float bowl 210 via line 202, fuel pump 204, line 205, fuelpressure regulator 206 and line 208. Float bowl 210 is quickly filled tothe operative level as controlled by float valve 218. During engineoperation valves 221 and 236 remain open and valve 223 remains closed.With valve 236 open, fuel vapors from tank 200 are vented to theoperating engine via line 234, valve 236, line 238, the vapor space offloat bowl 210 and internal vent 214'to the othercarburetor chambersyandare thus swept-into the combustion chamber'of the engine and burned.Closed valve 223 prevents any drainage from float bowl 210 to fuel tank200*during engine operation.

When the engine is shut off the conventional vacuum manifold of theinternal cornbustionengine returns to atmospheric pressure thusdissipating the vacuum source which was holding valve 223c1osed andvalves 221and 236 open. Valve 223' opens immediately, but the closing ofvalves 221 and 236 is delayed by the-action of vacuum reservoir tank244. In a fuel system as herein described, it is necessary that-tank2-00 be near or at the same pressure as float bowl 210 when drain-valve221 is open. Otherwise, there could be a reversesurge of fuel into floatbowl 210 which would prevent proper drainage and might even overflowinto the engine compartment resulting inan excessive hydrocarbon loss tothe atmosphere. Thus, tank vent valve 236 must remain'open as long asdrain valve 221 is open. When the engine vacuum manifold returns toatmospheric pressure, check valve 248 automatically closes thusallowingvacuum reservoir tank 244 to come gradually to atmosphericpressure with the entrance of air through orifice 252. The delay inclosing valve 221 and 236 is thus a function of the size of orifice 252and vacuum reservoir tank 244. An identical system was previouslydescribed in detail with relation to Figures 2 and 3.

When the pressure in vacuum reservoirtank 244'-ap proaches atmospheric,valves 22-1 and 236 close to seal the fuel tank from the atmosphereduring the engine-off period. When the engine is restarted, valves 221and 236 open and valve 223 closes by action of the engine vacuum sourceand the system repeats the first described mode of operation. Asdiscussed previously, thevacuum actuated valves illustarted in Figure4*can be electric solenoid valves, or mechanical valves, or electricvalves whose individual operation is controlled by the vacuum delaysystem shown-or'a conventional mechanical or electric delay system.

A further modification of our invention entails the use of' a levelingassembly 420, as shown in Figure 5. This leveling assembly adjusts thefuel level in the carburetor float bowl to any desired'level at the endof the drain period; Thus, fuel drains until the fuel level in floatbowl 408 is at the same level as weir 422 of leveling assembly 420. Asubstantial portion of the fuel 'can' therefore be removed from thefloat bowl, but-leaving enough-to initiate and support operation untilthe fuel pump can start refilling float bowl 408. Theco'mp'onent partsof the apparatus of Figure 5 and their arrangement and operation aresubstantially identical to the corresponding parts of Figure 1 exceptfor the added component of leveling assembly 420.

One method of operating the apparatus as shown in Figure 5 comprisesstarting engine operation with drain valve 426 closed and carburetorfloat bowl 4% partially empty, i.e.', fuel level at B--B. Fuel issupplied to carburetor float bowl 408 by fuel pump 404 via line 406which fills and maintains an adequate fuel reservoir through the actionof float valve 416. There is no flow of gasoline through the systemcomprising line 418, leveling assembly' 420, line 424, drain valve'426and line 428 during engine operation. When the engine'is stopped fuelpump 404 stops and therefore no longer supplies fuel via line 402 and406 to carburetor float bowl 408. Drain valve 426 is immediately openedupon engine stoppage, and float bowl 408 is partially drained to fueltank 400, via line 418, leveling assembly. 420, line 424, drain valve426 and'line 423. The drained level of float bowl 468 is at B-B which isdetermined by the relative position of overflow weir 422 of drainleveling assembly 420 With respect to float bowl 408. Overflow weir 422should be placed in level relationship with respect to the desired levelof the retained body of fuel in float bowl 408. Also, to minimizedrain-back from the fuel tank on steep inclines, drain levelassembly-420 can be placed near fuel tank 400, e.g., within the trunkcompartment of conventional automobiles. Drain valve 426 is then closedprior to or coincident with the resumption of engine operation. Theopening and closing of drain valve 426 can be effected by the engineintake manifold vacuum if it is a vacuum actuated valve, or, by theignition switch if a solenoid actuated valve, or manually if aconventional mechanical valve.

Fuel tank vent 434 and drain line vent 436 are both returned to the airintake channel of the carburetor immediately beneath where air cleaner414 is attached to carburetor body 410. Thus, there is communicationbetween the vapor space of fuel tank 400 and the throat of thecarburetor which,- during engine operation, will permit any vaporsevaporating from fuel tank 400 and drain line vent 436 to pass throughtank vent 434 to the throat of the carburetor where these vapors areswept into the engine combustion chamber and burned.

Although the fuel systems shown in Figures 1, 2, 3, 4 and 5 areillustrated with a single bowl carburetor, the method and apparatus ofour invention have been successfully applied to an engine having atwo-bowl carburetor, and any number of carburetors or bowls may beintegrated into the system.

The air pollution abatement device of this invention is rugged by virtueof its simplicity, but should any maintenance or repair work berequired, this can easily be accomplished since conventional parts,fittings, and equipment are used throughout.

While in the foregoing description, we have referred mainly tocarburetor fuel induction systems, the invention in its broadest aspectis not limited thereto. Other fuel induction devices, such as pressureinjectors may also draw from small intermediate fuel reservoirs locatedin the engine compartment. ,Our invention is hence applicable to anyfuel supply systems involving a storage tank relatively remote from theengine, and a secondary vented reservoir located sufficiently near theengine to absorb heat therefrom.

It will be apparent from the foregoing that the apparatus of ourinvention includes a new and novel carburetion device comprising ahousing enclosing an air-intake and fuel evaporation throat, anintegrally attached fuel reservoir chamber, a fuel inlet opening intothe reservoir chamber, at least one liquid fuel transfer port traversingthe housing and communicating the throat with the reservoir chamber,means for maintaining a substantially constant liquid fuel level in thereservoir chamber against a supernatant vapor space, at least onebalancing tube traversing the housing and connecting the supernatantvapor space in thefuel reservoir chamber with the throat, and a drainport opening from the bottom of the reservoir chamber.

While the method and apparatus of our invention deals primarily withsolving the evaporative loss problem by draining the fuel from the hightemperature vented chambers associated with the internal combustionengines, there are other approaches equally useful. All vents from thesefuel-containing chambers can also be shut ofi? from the atmosphere byappropriate valving during engine-off periods. This requires blocking 1)the internal vents, (2) the external vents, if any, and (3) in somecases the fuel conduit leading from the float chamber to the jet in thethroat of the carburetor. The fuel supply conduit to the float chamberconventionally has a check valve in it which will prevent flow backthrough the fuel pump. This closing in of the float chamber or anysimilar vented fuel reservoir can be accomplished either by modifyingexisting fuel induction systems or by incorporating the requisitevalves, manifolds, etc., into the design of new carburetors. The valvesused can be any conventional mechanical, vacuumoperated, or electricallyoperated valves, but preferably would be solenoid valves whose operationis controlled by the ignition switch. This sealing of the carburetorfuel reservoir chamber can be used in combination with all of themethods and apparatus described in relation to Figures 1, 2, 3, 4 and 5whereby pressures developed within the sealed off chambers can berelieved by transferring the fuel from the hot carburetor chamber tomore remote chambers.

Since the primary purpose of the draining is to keep the fuel in enginecompartment reservoirs, e.g., float chambers, cool during engine-offperiods, it is contemplated that any method of removing the fuel to acool space will accomplish the purpose of the invention, namelyreduction of evaporative loss during the hot soak" period. Thus, removalto a cool space can include transfer to any secondary reservoir or tothe main fuel storage tank with means provided for returning this fuelto the fuel induction system when the engine is started. Obviously,cooling of the fuel in the carburetor reservoir chambers in situ canalso reduce evaporative losses, and the isolation and insulation ofthese carburetor fuel chambers, i.e., float chambers and the like, cangreatly reduce the effect of the hot soak period. This application is acontinuation-in-part of our prior co-pending application Serial No.823,914, filed June 30, 1959.

Various other changes and modifications of this invention are apparentfrom the description of this invention and further modifications will beobvious to those skilled in the art. Such modifications and changes areintended to be included with the scope of this invention as defined bythe following claims.

We claim:

1. In combination with an internal combustion engine, an improved liquidfuel delivery and conservation system adapted to minimize evaporativefuel losses, comprising in combination a carburetor having a fuelreservoir chamber with at least one vent to the atmosphere, a fuelstorage tank, a pressure relief valve in the upper portion of saidstorage tank adapted to maintain a small maximum positive pressuretherein, a check valve in the upper portion of said storage tank adaptedto maintain at least atmospheric pressure therein, a fuel inlet port tosaid storage tank, a removable cap closing said fuel inlet port, a vaporconduit opening from said storage tank and communicating with theatmosphere, a vent valve in said vapor conduit, control means foractuating said vent valve, means for delivering fuel from said storagetank to said fuel reservoir chamber, a fluid drain conduit opening fromsaid fuel reservoir chamber and communicating with the interior of saidstorage tank and adapted to transfer fuel from said reservoir chamber tosaid storage tank when said fuel delivery means is inoperative, apressure relief vent line leading from an intermediate point in saiddrain conduit and communicating with the atmosphere, a first throttlevalve in said drain conduit, control means for actuating said firstthrottle valve, a second throttle valve in said drain conduit, controlmeans for actuating said second throttle valve, and a leveling assemblyassociated with said drain conduit comprising an overflow weir adaptedto maintain a minimum fuel level in said fuel reservoir chamber at alltimes.

2. In combination with an internal combustion engine, an improved fueldelivery and conservation system adapted to minimize evaporative fuellosses, comprising in combination a fuel induction device located nearsaid engine,

a fuel induction reservoir located near said engine and adapted todeliver fuel to said induction device, a remote fuel storage tank, meansfor delivering fuel from said storage tank to said induction reservoir,a vapor conduit opening from said storage tank to the vapor space insaid induction reservoir, a liquid drain conduit opening from saidinduction reservoir to said storage tank, means responsive to engineoperation for maintaining said drain conduit open for a short periodfollowing each cessation of engine operation and closed at all othertimes, and means responsive to engine operation for maintaining saidvapor conduit open during engine operation and a short time thereafterbut closed at all other times.

3. A combination as defined in claim 2 including means for confiningfuel vapors within said storage tank up to a pre-determined pressureduring periods when said drain conduit and vapor conduit are closed, andpressureresponsive means for exhausting fuel vapors therefrom at saidpre-determined pressure.

4. In combination with an internal combustion engine, an improved liquidfuel delivery and conservation system adapted to minimize evaporativefuel losses, comprising in combination a carburetor having a fuelreservoir chamber with at least one vent to the atmosphere, a fuelstorage tank, a pressure relief valve in the upper portion of saidstorage tank adapted to maintain a small maximum positive pressuretherein, a check valve in the upper portion of said storage tank adaptedto maintain at least atmospheric pressure therein, a vapor conduitopening from said storage tank leading into and communicating with thevapor space in said fuel reservoir chamber, a vent valve in said vaporconduit, means for maintaining said vent valve open when said engine isin operation and means for closing the same a short time after eachcessation of engine operation, means for delivering fuel from saidstorage tank to said fuel reservoir chamber, a fluid drain conduitopening from said fuel reservoir chamber and communicating with theinterior of said storage tank, said drain conduit being adapted totransfer fuel from said reservoir chamber to said storage tank when saidfuel delivery means is inoperative, a first throttle valve in said drainconduit, control means for maintaining said first throttle valve openduring operation of said engine and for closing the same a short timeafter each cessation of engine operation, a second throttle valve insaid drain conduit and control means for maintaining said secondthrottle valve closed during operation of said engine and for openingthe same substantially simultaneously with each cessation of engineoperation.

5. A combination as defined in claim 4 including a fuel inlet port tosaid storage tank and a removable cap closing said inlet port, andwherein said pressure relief valve and said check valve are positionedin said removable cap.

6. A combination as defined in claim 5 wherein said drain conduit isadapted to return fuel via said fuel inlet port to said storage tank.

7. A combination as defined in claim 4 wherein said reservoir chamber isvented only to the throat of said carburetor and contains no externalvents.

8. In combination with an internal combustion engine, an improved liquidfuel delivery and conservation system adapted to minimize evaporativefuel losses, comprising in combination a fuel storage tank, a pressurerelief valve in the upper portion of said storage tank adapted tomaintain a small maximum positive pressure therein, a check valve in theupper portion of said storage tank adapted to maintain at leastatmospheric pressure therein, a vapor conduit opening directly to theatmosphere from the upper portion of said storage tank, a vent valve insaid vapor conduit, means for maintaining said vent valve open for ashort time after each cessation of engine operation and closed at allother times, a carburetor having a fuel reservoir chamber with at leastone vent to the atmosphere, means for delivering fuel from said storagetank to said fuel reservoir chamber, a fluid drain conduit opening fromsaid fuel reservoir chamber and communicating with the interior of saidstorage tank, said drain conduit being adapted to return fuel to saidstorage tank when said fuel delivery means is inoperative, a throttlevalve in said drain conduit and control means for maintaining saidthrottle valve open for a short time after each cessation of engineoperation and closed at all other times.

9. A combination as defined in claim 8 including a fuel inlet port tosaid storage tank and a removable cap closing said inlet port, andwherein said pressure relief valve and said check valve are positionedin said removable cap.

10. A combination as defined in claim 9 wherein said drain conduit isadapted to return fuel via said fuel inlet port to said storage tank.

11. A combination as defined in claim 8 wherein said reservoir chamberis vented only to the throat of said carburetor and contains no externalvents.

12. In combination with an internal combustion engine, an improvedliquid fuel delivery and conservation system adapted to minimizeevaporative fuel losses, comprising in combination a remote fuel storagetank, a fuel induction device associated with said engine, an inductionsystem fuel reservoir chamber located near said engine and having atleast one vent to the atmosphere, fuel delivery means for deliveringfuel from said storage tank to said fuel reservoir chamber, means fortransferring fuel from said reservoir chamber to said fuel inductiondevice, a fluid drain conduit opening from said fuel reservoir chamberand communicating with the interior of said storage tank, said drainconduit being adapted to return fuel to said storage tank from saidreservoir chamher when said fuel delivery means is inoperative, andmeans for maintaining a minimum fuel level in said fuel reservoirchamber at all times.

13. A combination as defined in claim l2 wherein said means formaintaining a minimum fuel level comprises a leveling assemblyassociated with said drain conduit, said leveling assembly comprising anoverflow weir adapted to maintain a minimum fuel level in said fuelreservoir chamber at all times.

14. A combination as defined in claim 12 wherein said fuel inductiondevice is a carburetor, and said induction system fuel reservoir chamberis a float chamber provided with a fioat valve therein for controllingthe rate of fuel delivery to maintain a constant liquid level therein.

15. A combination as defined in claim 14 wherein said fuel reservoirchamber is vented only to the throat of said carburetor and contains noexternal vents.

16. A combination as defined in claim 12 including a pressure reliefvent line leading from an intermediate point in said drain conduit andcommunicating with the atmosphere,

17. A combination as defined in claim 12 including a vent communicatingwith the atmosphere from the vapor space in said fuel storage tank.

18. A method for reducing fuel evaporation in the fuel supply system ofan internal combustion engine having a carburetor with a fuel reservoirchamber vented to the atmosphere, which method comprises emptying saidchamber and returning drained fuel to the fuel storage tank immediatelyafter stopping said engine, sealing the fuel storage tank from theatmosphere a short time after draining said fuel reservoir chamber, andventing said fuel storage tank to the atmosphere immediately uponstarting said engine.

19. A method for reducing fuel evaporation in the fuel supply system ofan internal combustion engine having a carburetor with a fuel reservoirchamber vented to the atmosphere, which method comprises partiallydraining said chamber of retained fuel to the fuel storage tankimmediately after stopping said engine and maintaining at least aminimum fuel level within said fuel reservoir chamber at all timeswhereby the engine has fuel available for immediate starting.

20. A method for reducing fuel evaporation from the fuel supply systemof an internal combustion engine having a carburetor with a fuelreservoir chamber vented to the atmosphere, which method comprisesemptying said chamber by draining retained fuel to the fuel storage tankimmediately after stopping said engine, venting the fuel storage tank tothe atmosphere while the fuel reservoir chamber is being drained, andmaintaining said fuel storage tank closed to the atmosphere at all othertimes.

21. A combination as defined in claim 2 wherein said vapor conduitconsists essentially of an internal vent line leading from saidinduction reservoir to the air intake channel of said fuel inductiondevice, and a storage tank vent line leading from said storage tank tosaid air intake channel, said engine-responsive means being located insaid storage tank vent line.

2 A method as defined in claim 18 wherein said fuel reservoir chamberand said fuel storage tank are each vented to the atmosphere solelythrough an air intake channel of said carburetor.

References Cited in the file of this patent UNITED STATES PATENTS1,909,390 Ball May 16, 1933

